# std::scoped_allocator_adaptor<OuterAlloc,InnerAlloc...>::outermost, outermost-construct, outermost-destroy

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< cpp‎ | memory‎ | scoped allocator adaptor

template< class Alloc > /* unspecified */ /*outermost*/( Alloc&& alloc = *this ); | (1) | (exposition only*)
template< class T, class... Args > void /*outermost-construct*/( T* p, Args&&... args ); | (2) | (exposition only*)
template< class T > void /*outermost-destroy*/( T* p ); | (3) | (exposition only*)

These exposition-only helper member function templates are used in member functions `construct()` and `destroy()`.

1) Obtains the outermost allocator of alloc.

- If the expression alloc.outer_allocator() is valid, returns `outermost`﻿(alloc.outer_allocator()).
- Otherwise, returns alloc.

2,3) Constructs or destroys an object using the outermost allocator of *this.
Given the type std::allocator_traits<std::remove_reference_t<decltype(`outermost`﻿())>> as `outermost_traits`:
2) Equivalent to outermost_traits::construct(`outermost`﻿(), p, std::forward<Args>(args)...);.
3) Equivalent to outermost_traits::destroy(`outermost`﻿(), p);.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 3116 | C++11 | the recursion condition for `outermost` was “alloc has the member function `outer_allocator()`” | changed to “the expression alloc.outer_allocator() is valid”

### See also

construct [static] | constructs an object in the allocated storage (function template)
destroy [static] | destructs an object stored in the allocated storage (function template)

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